Antenna base



FIG. 1 is a front elevational view of an antenna base showing my new design, with the broken line satellite dish included for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a top plan view;

FIG. 3 is a right side elevational view;

FIG. 4 is a rear elevational view;

FIG. 5 is a left side elevational view; and

FIG. 6 is a bottom plan view. 

The ornamental design for antenna base, substantially as shown and described. 